Hybrids between mouse hepatoma cells and human leukocytes have been shown to secrete human serum albumin. I plan to use somatic cell hybrids between murine hepatoma lines and human diploid ones to map the structural loci for human albumin, transferrin, alpha-1 antitrypsin, and ceruloplasmin. Other human cell proteins will be mapped using two-dimensional electrophoresis. The phenomenon of activation of human albumin will be studied to determine the kind of genetic components involved in expression of this human gene. Variants of the hepatoma line that fail to secrete albumin will be used in complementation analysis to determine the number and kinds of loci governing albumin production. These same cells will be used to identify and map human genes involved in albumin secretion. Finally, embryonic cells at various developmental stages will be tested for their capacity to express organ specific functions following hybridization with differentiated hepatoma cells.